The present invention relates to vehicle entranceways and exitways and, particularly, to stowable ramps associated therewith for facilitating the passage therethrough of wheelchairs and persons unable to negotiate one or more steps up into the vehicle.
There has long been a need for an extendible ramp at the entranceway of a motor bus, for example, over which a wheelchair passenger or other handicapped person might traverse in entering or leaving the vehicle at a bus stop. Several years ago, one of the inventors of the subject application was granted U.S. Pat. No. 4,131,209 covering such an extendible ramp device. Even though this earlier device was a distinct improvement over prior art ramps, certain further improvements in this device were necessary and are the subject of the present invention.
In the predecessor patented device, the ramp actuating electric motor and drive screw were incorporated into the ramp structure itself which created several potential problems. First, this increased the mass or weight of the ramp structure and, thus, either required a larger motor than necessary to move the ramp alone or reduced the rate at which the ramp could be extended or retracted relative to the vehicle. Next, being part of the extendible ramp structure subjected both the electric motor and the drive screw to potential damage. Finally, in the earlier design it was necessary to create a hump or a housing in the pivotal riser member to accomodate the motor and which housing could interfere with the passage of a wheelchair or otherwise impede the passage of a handicapped person.